Follow-up



March 19, 1940. w. H. NEWELL FOLLOW-UP Filed 001;. 11, 1938 IN VENTOR Elwin/Bu v ATTORNEY Patented Mar. is, 1940 UNITED STATES PATENT OFFICE Instrument Company, N. Y., a corporation of Application October 11, 1938, Serial No.

4 Claims.

This invention relates to a receiver mechanism of the follow-up type and particularly to the type utilized with electrical transmission systems for driving an object in response to movement of a controlling object and accompanied by an amplification of the power applied to the controlled object. More specifically this invention relates to the control of a servo-motor in systems of this type for driving an object in response to theaction of dual high and low speed self-synchronous systems.

Where it is desired to transmit angular motions accurately, it is common to use two selfsynchronous systems. With one of these systems, the transmitter is operated in a one to one ratio with the controlling object, and the transmitter of the other system. is operated in a higher ratio with respect to the controlling object. The receivers of these two systems are thus actuated in accordance with their transmitters and their respective ratios with respect to the controlling object. In systems in which the receivers are arranged to control the operation of a prime mover to effect movement of a driven object in accordance with the movement of the controlled object, the receiver actuated in a ratio of one to one with the driven object takes predominance in the control of the follow-up prime mover, in that it assumes control as soon as the disagreement in position between the driving and driven members exceeds a certain amount. In such systems as have heretofore been used, it has been necessary to utilize. complicated relays or mechanical connections between the receivers of the self-synchronous systems or between these receivers and the servo-motor, the energization of which they control.

It is an object of this invention to provide a receiving mechanism by means of which a sensitive control of the driven object can be had throughout the range of movement of the controlling object without resorting to the use of mechanical or electrical relays or transfers of any kind between the control contacts corresponding to the coarse or fine adjustment receivers. The arrangement is of simple construction and has a relatively small number of mechanical elements for actuating the necessary electrical contacts for controlling the servomotor.

In accordance with the provisions of the invention these objects are accomplished by the use of a capacitor type servo-motor adapted to be operated by a pair of control circuits arranged tlon A. The mechanism so Inc., Long Island City, New York to conjointly and independently control the energization of this motor. These circuits are controlled by coarse and fine adjustment receivers so that when both of these receivers are acting conjointly, the motor will be controlled to operate in accordance with the actuation of the coarse adjustment receiver.

The invention together with the objects and advantages thereof will be more fully understood upon reference to the following description and the accompanying drawing of which the single figure shows diagrammatically a position reproducing system embodying the invention.

Referring to the single figure, A designates a transmitting station capable of being adjusted to any desired position with reference to a pointer 2 by means of an adjusting device or handle I. The transmitting station A consists of transmitters 3 and 4 which may be geared together so that one system, the one including the transmitter 4 makes thirty-six revolutions while the System including the transmitter 3 makes one revolution. The transmitting elements 3 and 4 are connected by wires 5 and 6 to the receivers l and 8 respectively, which receivers form a receiving station at B for the transmitting stafar described consists of two self-synchronous transmission systems of the type well known in the art and their detail description and illustration has been omitted.

When the handle I of the transmitter A is moved .to a position, with reference to the pointer 2, the transmitters 3 and 4 (referred to hereinafter as the transmitting elements for coarse and fine adjustment respectively) effect in a well known manner rotation of the rotors of the receivers 1 and 8, which will hereinafter be referred to as the receivers for coarse and fine adjustment respectively.

The stators of the receivers l and 8 are connected by gears 9 and I9 respectively and a gear train H to a shaft 12 carrying 'a worm gear 13 which is connected by means ofa pinion l4 and a shaft l5 to an indicator dial C. The shaft I2 is also rotatably connected to a servo- 5 motor M, of a reversible, capacitor type having coils N and O which are connected to receive electrical energy from line wires l1 and 18, by means of wires I9, 20, 2|, 22 and 23. A capacity, or condenser P, is connected across the coils 5 N and O of the motor M. Another condenser Q is connected in series with an inductance R and they are connected in series across the linewires i1 and it! by means of the wires 22 and 23.

The motor M is controlled by two sets of contacts, each set independently adapted to effect the operation of the motor. One of these sets of contacts comprises a movable contact arm 24, connected to the rotor of the coarse adjustment receiver l by means of a shaft 26, and operatively associated with stationary contacts S and T (referred to hereinafter as the coarse contacts). Contacts S and T are connected to wires 20 and 21 respectively, in the circuit of the motor M. The other set of contacts includes another movable contact arm 25, connected to the rotorv of the fine adjustment receiver 8 by means of a shaft 2?, and operatively associated With stationary contacts U and V (referred to hereinafter as the fine contacts). Contacts U and V are connected to the wires 20 and. 2t respectively in the circuit of the motor M.

When the receivers for the coarse and fine adjustment are operating conjointly to control the operation of the motor M, the condenser Q, connected in series with the contact arm 25, causes the motor M to operate in accordance with the actuation of the coarse adjustment receiver. The movable contact arms 24 and 25 are coupled to the outer ends of the shafts 26 and 2'! respectively by means of yieldable cam couplings 26a and 21a, by means of which these arms are kept in proper relation with their appropriate contacts during each half revolution of their respective rotors. Such a coupling permits relative movement of the rotor and the contact arm connected thereto, .but reverses the contact arm every half revolution of such relative,

movement. By this means the motor is controlled to drive the driven object by the most direct path into positional agreement with the controlling object. This yieldable coupling is particularly desirable when both coarse and fine adjustment receivers are used, since it permits relative motion between the rotor and contact arm of the fine adjustment receiver during the period in which the servo-motor operates under the control of the coarse receiver.

In operation of the system when the transmitter A is moved by means of the handle I to a new position, with reference to the pointer 2, the rotors of the receivers 1 and 8 will follow this movement in accordance with their respective ratios with respect to the handle I. The

contact arms 24 and 25 are thus moved to effect energization of the motor M by completing the circuit to the motor. The rotation of the motor M, its shaft l2 and worm i3 drives pinion l4 and load shaft I5' and incidentally turns the indicator dial C to a point with reference to the pointer l6 which is in positional agreement with that of the dial of the transmitter A. At the same time the motor M also drives the stators of the receivers 7 and 8, through the gear train II and gears 9 and II] respectively, in directions opposite to the movements of their rotors, whereby the rotors are restored to their original angular position between the contacts.

Assume, for example, that the handle I of the transmitter A is moved to a new position with reference to the pointer 2 corresponding to a small angular movement of say, several degrees, in a direction so that the fine contact arm 25 will make connection with the fine contact V. A control circuit is thereby closed from this contact as follows: Line wire l1, wire 22, condenser Q, contact arm 25,;contact V, wire 2|, coil (and condenser P and coil N), wire I9 to line wire Is.

This will cause the motor M to operate in one direction. For an equal angular movement of the handle I of the transmitter A in the opposite direction, the rotation of the motor M will be reversed, since the contact arm 25 will make connection with the opposite fine contact U.

For a larger angular movement of the transmitter A, corresponding to a movement of say, 100 degrees in such a direction that the arm 24 makes the coarse contact T, a control circuit is thereby closed from this contact as followsrLine wire l1, wire 22, contact arm 24, contact T, wire 2|, motor coil 0 (and condenser P and coil N) and wire is to line wire l8. The receiver and the contact arm 25 of the fine receiver will be moving back and forth with each of travel (assuming a ratio of 36 to- 1 in the gears between the fine and coarse transmitters), making contact alternately on fine contacts U and V. When the contact is made on fine contact U, the condensers Q and P are connected in parallel, putting the sum of their capacities in the supply to the motor M. When the contact is made on the fine contact V, the condenser Q is paralleled and has no efiect.

While the use of the condenser Q in the circuit described above provides a Satisfactory system, the addition of the inductance R, in proper value and connected in as illustrated, results in a better operation over a greater range of conditions, and particularly is this true when the coarse and fine contacts are operating on opposite sides of the motor. The general purpose of inductance R is to increase the inductance in proportion to the increase of capacity by the inclusion of capacity Q.

From the foregoing description it will be apparent that a reproducing system is provided by means of which a sensitive control of the driven object is had throughout the total range of movement of the controlling object. The mechanism is simple of construction, and has but a few mechanical elements for controlling the servo-motor.' The foregoing is accomplished by the elimination of electrical or mechanical transfers between the coarse and fine contacts.

While a preferred embodiment of the invention has been shown and described, it will be understood that the invention may be embodied in other forms and that various changes may be made in the structural details without departing from its principles as defined in the appended claims.

I claim:

1. An electrical system for reproducing angular position comprising a coarse adjustment transmitter and receiver and a fine adjustment transmitter and receiver, a follow-up motor of the single phase, alternating current capacitor type, a motor circuit, two pairs of contacts connected in parallel in the motor circuit, a cooperative contact for each pair of contacts controlled by one of the receivers, and a separate capacity in circuit with one of the cooperative contacts.

2. An electric system for reproducingangular position comprising in combination, a transmitting element for fine adjustment, a transmitting element for coarse adjustment, corresponding receiver elements respectively connected to said transmitting elements, a reversible capacitor type electrical motor, a pair of control means, each independently operative to effect the operation of the motor including a pair of electrical circuits each comprising relatively movable contacts for controlling the energization thereof, a connection for effecting the relative movement of the,

1 will be driving contacts of one circuit by the fine adjustment 7:;

receiver, a connection for effecting the relative movement of the contacts of the other circuit by the coarse adjustment receiver, and a condenser in one of said circuits for causing the motor to operate in accordance with the coarse adjustment receiver upon conjoint energization of the said circuits.

3. An electric system for reproducing angular position comprising in combination, a transmitting element for fine adjustment, 2. transmitting element for coarse adjustment, corresponding receiver elements respectively connected to said transmitting elements, a reversible capacitor type electrical motor, a pair of control means, each independently operative to effect the operation of the motor including a pair of electrical circuits each comprising relatively movable contacts for controlling the energization thereof, a connection for effecting the relative movement of the contacts of one circuit by the fine adjustment receiver, a connection for effecting the relative movement of the contacts 01 the other circuit by the coarse adjustment receiver, and a condenser and a reactance for causing the motor to operate in accordance with the coarse adjustment receiver upon conjoint energization of the said circuits.

4. An electrical system for reproducing angular position comprising in combination, a transmitting element for fine adjustment, a transmitting element for coarse adjustment, corresponding receiver elements respectively connected to said transmitting elements, a reversible capacitor typev electric motor, a pair of control means each independently operable to efiect the operation of the motor and including relatively movable contacts, a connection for effecting relative movement of the contacts of one control means by the relative angular position of the fine adjustment receiver and the motor, a connection for efiecting relative movement of the contacts of the other control means by the relative angular position of the coarse adjustment receiver and the motor, and a condenser in circuit with the contacts of the control means operated by the fine adjustment receiver .for causing the motor to operate in accordance with the coarse adjustment receiver upon conjoint energization of the two control means.

WmrIAMI-LNEWEE 25 

